Round balers generally have a bale forming chamber defined by a pair of opposing side walls associated with an array of side-by-side belts, transverse slats trained on chains, a plurality of transverse rolls or a combination of these various elements, e.g., rolls and belts. During field operation, windrowed crop material such as hay is picked up from the ground and fed in a continuous stream into a fixed or variable diameter chamber. The hay is rolled into a cylindrical package within the chamber, wrapped with twine, net or the like and ejected onto the ground for subsequent handling.
U.S. Pat. No. 5,444,969, issued Aug. 29, 1995 in the name of Robert A. Wagstaff, et al, discloses a prior art round baler of the general nature described above. In this particular type of baler an expandable chamber is defined by a pair of sidewalls, and a plurality of side-by-side belts cooperating with a series of transverse rolls, mounted between a pair of pivotally mounted arms. The chamber includes an inlet opening in the front through which crop material is fed. The aforementioned arrangement of rolls and arms is commonly referred to as a sledge assembly. Also shown in the disclosed baler is a pair of take up arms pivotally mounted on the main frame, between which arms a pair of guide rolls are journalled. The outer surfaces of the guide rolls are urged against the belts to maintain belt tension and thereby prevent slack from occurring in the belts during expansion and contraction of the chamber. General arrangements of this nature are commonly referred to as apron tensioning systems.
Examples of prior art tensioning systems used in round balers of the general type shown in the '969 patent, are disclosed in U.S. Pat. No. 5,014,613, issued May 14, 1991 in the name of John H. Merritt, et al, U.S. Pat. No. 5,327,821, issued Jul. 12, 1994 in the name of John R. McClure, et al, and U.S. Pat. No. 5,367,865, issued Nov. 29, 1994 in the name of Richard E. Jennings, et al. In U.S. Pat. No. 5,014,613 the apron tensioning system shown employs a spring and pivot arm combination, while in U.S. Pat. No. 5,327,821 a system is shown that utilizes an hydraulic cylinder in combination with a pivot arm assembly. The tensioning mechanism in the U.S. Pat. No. 5,014,613 discloses a prior art system in which both a spring and an hydraulic cylinder are used.
In the three aforementioned apron tensioning systems, the elements are all mounted outwardly of the sidewalls of the balers. In another prior art baler an apron tensioning cylinder is centrally mounted on the front of the frame, e.g., see French brochure No. F-8602BP, printed in Holland in 1986 by the PZ Zweegers Company. This brochure is entitled "PZ Zweegers ROBALL(R) 1512 PRESSE A BALLES Rondes". It should be noted that the baler shown in this brochure is a belt type baler, i.e., the expandable chamber is defined only by belts, as opposed to rolls and belts.
The present invention relates to apron tensioning for a round baler in which a cylindrical package of crop material is formed between expandable walls consisting of a combination of belts and rolls of the general nature described in the '969 patent, cited above. This patent is an example of many prior art patents, assigned to New Holland North America, Inc., that disclose this type of round baler, referred to by some as a roll belt round baler. Unique structural characteristics, described below, contribute to a round baler having an apron tensioning system that, among other things, enhances performance, simplifies construction and improves durability. Additionally, there is a noted improvement in the appearance and density of round bales formed by the baler of the present invention.